Balanced slide-valve



(No Model.)

2 Sheets-Sheet 1.v F. M. RITES. BALANGED'SLIDE VALVE.

Patented July 18, 1893 .mw F

WITNESSES:

o t e e .h s s t e e h s 9.

E V .L Sn Uu TE TLD vM RS Mm .m PMA .ML A B .u d 0 M 0 N Patented July18, 1893.

WI'I'N ESSES:

BNVENTOR,

UNITED STATI-34s PATENT OFFICE.

FRANCIS M. RITES, OF ALLEGI-IENY, PENNSYLVANIA.

BALAN GED S Ll DE-VALV..

SPECIFICATION forming part of Letters Patent No. 501,663, dated July18,' 1893.

Application filedMarchlS, 1893.

To all whom it may concern.-

Be it .known`that I, FRANCIS M. RITEs, a citizen of the United States,residing at Allegheny, in the county of Allegheny and State ofPennsylvania, have invented or discovered a certain new and usefulImprovement in Means for Balancing Slide-Valves, of which improvementthe following isa specification.

My invention relates to the operation of steam distribution valves ofthe slide type, in which the back ofthe valve is ordinarilysubjected tothe pressure of the steam in the chest or chamber 2within which thevalve moves, such pressure tending, particularly in the case of valvesof comparatively large dimensions, to create excessive friction betweenthe sliding surfaces of contact,.unless means for its relief orcounteraction is provided. Numerous devices for this purpose haveheretofore been proposed and applied in practice with varying degrees ofsuccess, Vthese being generally in the nature of pressure plates,balancing plates, or inclosed chambers,.upon which the steam pressure isexerted, and by which the valve is relieved, to a greater or lessextent, therefrom. The character of these appliances has generally beensuch that they are subject to the objections of interfering with thefree passage of steam and of involving complication and liability toderangement of parts.

The object of my invention is to admit of the unrestrained exertion ofsteam pressure upon the entire area of the back of the valve, and of thefree and unimpeded circulation of steam over and around the same, Whilepreventing the objectionable friction of the sliding surfaces in contactbefore referred to, by counteracting the pressure on the back of thevalve, as varied from time to time in its operation, by oppositelyacting and correspondingly Varied pressure.

The improvement claimed is hereinafter fully set forth.

While my invention is readily and advantageously applicable in singlecylinder or simple engines in which slide distribution valvesare-employed, its practice will'be found more particularly desirable inmultiple cylinder engines, and will be herein exemplied in an engine ofsuch type, as applied in connection .with the slide distribution valveof the last Serial No. 465,674. (No model.)

or low pressure cylinder. In such cae, a materially higher pressurethanthat in the receiver, which acts upon theback of the valve, beingdirectly available from thel boiler, which is the source of highpressure supply, only a comparatively smallspace or-recess beneath thevalve will be requiredfor the eX- ertion of the requisite balancingpressure.`

In the accompanying drawings: Figure 1 is a transverse section, at theline of Fig. 2, through the low pressure cylinder, low press uredistribution valve, valve chest, andexhaust passage of a tandem compoundengine, illustrating an application of my invention; Fig. 2, alongitudinal central-section through the cylinders, valve chests,receiver, and valves; and, Fig. 3,-a similarsection, on an enlargedscale, through a valvular appliance employed for effecting andregulating the application of supplemental pressure to the'low pressurevalve. i

My invention is herein illustrated as applied in a tandem compoundengine having a high pressure cylinder 1 and a lovvr pressure cylinder2, fitted, respectively, with pistons 3 and 4, which are-secured upon apiston rod 5. The distribution functions of the high pressure cylinder`1 are effected by a hollow or tubular distribution valve 6, of thepiston type, which is reciprocated by suitable valve gear, connected toits stem 7, in a bushing 8, located within a high pressure valve chest9, to which steam from the boiler is supplied through a steam supplyconnection 10. high pressure valve 6 is provided with end pistons 1l,12, which control, respectively, induction and eduction ports 13, 14,formed in the bushing 8, and in the adjacent portions of the shell ofthe high -pressure cylinder 1. The low pressure cylinder 2 is providedwith a slide distribution valve 15, reciprocated, within a valve chest16, by valve gear connected to its stem 17. The valve 15 controlsinduction and eduction ports 18, 19, in `the shell of the low pressurecylinder, and its eX- haust cavity or recess 20, which is closed at itsinner side, or that nearest the cylinder, for the major portion of itslength and breadth, communicates continuously with an exhaust port 21,to which is connected an exhaust port leading to the atmosphere or to acondenser, as the case may be. The high pressure and The- IOO

low pressure valve chest 9 and 16 communicate directly one with theother, and the space within the high pressure chest at the ends of thevalve 6 and within the tubular body and pistons of said valve, togetherwith that within the low pressure chest on the outside of the valve 15,form a receiver, through which steam is expanded from the high pressureto the low pressure cylinder.

For lthe practice of my inventioml lform on the inner 0r face side ofthe slide valve 15, a balancing chamber or recess 22, which is open tothe valve face, and is closed and separated from the exhaust recess 2Oof the valve, by its back, end, and side walls, the inner surfaces, ofwhich abut against and slide on the valve face. The area of the insideof the back wall of the balancing chamber must obviously be less thanthat of the back of the valve, by reason of the length and breadth ofthe balancing chamber being limited by the necessity of providing properports and lips in the valve for establishing communication between thevalve chest and the cylinder ports 18 and 19, and between said cylinderports and the exhaust port 21, through the exhaust recess 20. The backof the valve 15 will, therefore, be of correspondingly greater lengthand width than the balancing chamber. In order to counteract thepressure in the valve chest 16, which acts to press the valve 15 againstthe valve face, iiuid under pressure is admitted to the balancingchamber 22, through a supply pipe 26, the pressure of said fluid actingon the valve in reverse direction to the pressure in the valve chest,and being greater than that of the steam in the valve chest, in inverseproportion to the areas of the inside of the back wall of the balancingchamber 22 and of the back of the valve 15 respectively.

Inasmuch as the pressure in the valve chest will vary, from time totime,in the operation of the engine, in accordance with variations ofthe point of cut off, and under some circumstances may be negative, asubstantial equalization of the pressures, acting on the balancingchamber and on the back of the valve respectively, is maintained byvarying the former pressure coincidently with and proportionately tovariations of the latter, and to maintain the valve in vcontact with thevalve face, under certain conditions, supplemental pressure is appliedto the back of the valve. For example, in an engine of the typeillustrated, as the high pressure cut off is lengthened to meet anincrease in the load of the engine, the receiver pressure alsoincreases, and a corresponding greater pressure in the balancing chamberis, therefore, required and furnished to counteract it. Again, if afterthe valve has been properly balanced, the degree of vacuum in theexhaust passage is lowered, or back pressure in the exhaust passage isexerted, the supply of pressure to the balancing chamber iscorrespondingly reduced,or completely cut olf, as the case may be, tomaintain equilibrium of pressure upon the pressure,

valve. It may, further, be found, that atrare intervals, and when theloadV of the engine suddenly becomes very light, the governor willentirely cut off steam from the high pressure cylinder, in which case apartial vacuum will bev formed in the receiver,- and the valve will tendto be lifted from its seat. fluid under pressure is admitted to thevalve chest, to exert a pressure therein acting in opposite direction tothe pressure in the exhaust recess or beneath the valve, and thereby tomaintain, as nearly as may be,an equilibrium of opposing pressures. vTheservice of the conditions of outward pressure beneath the valve does notinvolve waste or constant expenditure of steam or other fluid underpressure, as such fluid is not discharged, but acts in the manner of aninner bearing or support for the valve, which may be said to float uponit. In the isolated instances in which fluid under pressure is suppliedto the valve chest, as above noted, such Huid is, of course, used andexhausted.

In order to effect and regulate the supplemental supply of steam orother fluid under as above noted, which is a leading and characteristicfeature of my invention, I provide a valvular appliance, an example ofwhich is clearly shown in Fig. 3, and which is substantially of thefollowing construction. A casing or chest 23, is fitted with threepistons, 28, 29, 30, which are connected, so as to be movablesimultaneously in the direction of the length of the casing, by beingformed or fixed upon a central rod or stem 31. The pistons 29 and 30 areof equal diameters, and the piston 28 is of smaller diameter than thepistons 29 and 30. Modifying pressure, tending to force the pistonseither to the right or to the left, may be exerted on the piston 28 byahelical spring 35, the tension of which can be varied as desired by ahand adjusting rod 37, passing through a suitably packed stuffing box 38in the left hand end of the casing and having a screw thread engagingwith the cap thereof, said rod abutting against a plate 36, which isconnected to the adjacent end of the spring 35. A fluid supply pipe 24,leading from a source of liuid pressure greater than that in the lowpressure valve chest, being, preferably, the boiler, opens into a sidepassage in the casing, having en d ports 32, 33, one of which, 32, opensaround the bore fitted by the piston 28, and the other, 33, opensbetween the pistons 29 and 30. A pipe 25 leading from the receiver, thatis to say, from any portion of the receiver space in the valve chestspreviously specified, opens into the end of the casing 23 adjacent tothe piston 30, which controls communication between said pipe and theport 33, through an opening 34:, in which said piston normally fits andwhich it normally closes. A pipe 26 leads outwardly from the spacebetween the pistons 28 and 29, and discharges into the balancing chamber22 of the low pressure valve, and a pipe 27 leads from the space at theouter end In such case IOC of the piston 2S to a point which isconstantly in communication with the exhaust recess 20 Y of the lowpressure valve l5.

Under a construction substantially as above described, the spring 35 isso adjusted that the ordinary normal pressure in the receiver, will, byits action upon the piston 30, force the series of pistons to the left,against the resistance of the spring 35, and will cause the piston 28 toopen the port 32 sufficiently far to admit pressure steam to the pipe 26and balancing chamber 22, at such pressure as will counteract thepressure on the back of the valve 15. Increase or decrease of reservoirpressure will effect a corresponding increase or decrease of opening ofthe port 32 and of supply to the balancing chamber. The reduction of thedegree of vacuum in the exhaust passage or the institution of backpressure therein, imposes additional pressure upon the piston 28 andcorrespondingly acts to reduce or cut 0E the supply through the port 32and pipe 26 to the balancing chamber. In each case, however, adetermined ratio between the pressures above and below the valve ismaintained by the reaction of the latter pressure through the dierentialareas of the pistons, in unison with the exhaust pressure but inopposition tothe receiver pressure, while an excessive reduction ofreceiver pressure, moves the pistons sufficiently far to the right toclose the port 32 and cut oft communication with the balancing chamber,and also to open the passage 3a and admit steam from the pipe 24,through said passage, and through the pipe 25, to the receiver.

The provision of the two independent larger pistons 29 and 30, and theintermediate supply port 32, is made for the purpose of causing theautomatic admission of high pressure Huid to the low pressure valvechest, when, as before explained, a partial vacuum happens to be formedtherein. It will, however, be readily seen that the performance of suchfunction, while necessary to the full embodiment of my invention, may,if desired, be dispensed with, in view of the comparative infrequency ofthe conditions under which it is called for. A construction therefore,of the valvular appliance, in which a single larger piston is employedin lieu of the two pistons 29 and 30 of the example herein shown, andthe port 33 is dispensed with, would be within the spirit and governingprinciple of my invention, and would perform all the functions of theappliance shown, except that of high pressure admission to the valvechest.

In the application of my invention to simple or single expansionengines, it will be obvious that the fluid supplied to the balancingchamber must be at a pressure higher than,

that in the boiler, or the balancing eect be only partial. Such increaseof pressure may be readily and conveniently effected by the employmentof a device such as a small force pump worked by the engine, and actingto compress any suitable uid, or to impose pressure vupon an inelasticduid, within the the balancing chamber of the valve.

I claim as my invention and desire to secure by Letters Patent 1. Thecombination of a slide distribution valve having a balancing chamber orrecess in its face, a valve chest, a valve face, a iiuid supply passagehaving its discharge opening in that portion of the valve face which iscontinuously covered by the valve when in operation, and a valvularappliance having differential pistons subject to pressure, in onedirection from steam in the valve chest,and in the other to pressurefrom the exhaust steam, and being intermediately subject to pressurefrom a source of high pressure supply, said pistons controllingcommunication between said source of high pressure supply and thebalancing chamber, substantially as set forth.

2. The combination of a slide distribution valve having a balancingchamber or recess in its face, and a valvular appliance consisting of acasing or chest, a smaller piston and two larger and equal sized pistonsmounted on the same stem and adapted to move longitudinally in thecasing, a passage leading from the chest, on the outer side of thesmaller piston, to the exhaust passage controlled by the distributionvalve, ports leading from a high pressure supply into the casing betweenthe two larger pistons and between the smaller piston and one of thelarger pistons respectively, a passage leading from the casing, betweenthe smaller and one of the larger pisl tons, to the balancing chamber ofthe distribution valve, a passage leading from the casing on the side ofthe larger piston farthest from the smaller piston to the valve chest,and an opening controlled by said larger piston establishingcommunication between one of the high pressure supply ports and saidvalve chest passage, substantially as set forth.

In testimony whereof I have hereunto set my hand.

FRANCIS M. lRI'IES. Witnesses: J. SNowDEN BELL, R. H. WHITTLESEY.

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